This invention relates to apparatus for mounting the actuator and trim on a valve and is particularly suitable for undersea applications.
It is often desirable in the production of oil and gas from subsea wells to provide flow control valves at the wellhead at the sea floor. Such valves are usually operated, maintained or repaired manually or with submersible vehicles that have limited capability.
For example, in one embodiment a four inch cage and plug type valve body is mounted in piping at a subsea wellhead. The "trim" or operating mechanism within the valve body is replaceable so that leakage or wear problems can be rectified. A valve actuator or operator is commonly connected to the trim so that the valve can either be operated from a remote location or it can be operated manually with relatively little effort. In such an arrangement the valve trim and actuator are ordinarily removable from the valve as a unit for return to the tender or platform for maintenance. In an exemplary embodiment the dry weight of the trim and actuator is about 335 kilograms. This heavy assembly must be secured to the valve body by divers or submersibles.
Previous arrangements for making this connection have not been entirely satisfactory. The actuator and trim may be connected to the valve body by flanges which requires the assembly and tightening of a large number of bolts. The bolts must be removed when the valve is disassembled for maintenance. In another arrangement the valve body is threaded and a "hammer nut" is used to secure the trim in the valve body. As suggested by its name, the nut is tightened or loosened by hammering.
There are clear shortcomings to either of these approaches and it is therefore desirable to provide a means for reliably and easily connecting the trim and actuator to a subsea valve. It is desirable that this be simple so that a single diver can perform the operation quickly and with minimum effort.